Technical-economic analysis of electric furnaces for gas nitriding

Abstract

1. To reduce nitriding costs it is necessary to select a furnace from comparison of unit costs for electricity, gas, maintenance, etc., for furnaces of different types and sizes. 2. The most economical of all the furnaces used in industry are electric shaft furnaces. 3. Furnaces with a moveable chamber are the most expensive. With a large volume of production they can be replaced with multibed bell furnaces (if shaft furnaces cannot be used), which makes it possible to increase the output of the furnace by a factor of at least two and reduce the cost of nitriding by at least 13–20%. 4. With a substantial volume of production it is inefficient shaft furnaces with V<0.6 m3. 5. The use of the semicontinuous process in furnaces of various types reduces the specific expenditure of electrical energy by 15–30%, reduces the specific expenditure of gas, increases the output of the furnace, and reduces the cost of nitriding. 6. With increasing outputs and lower nitriding costs in large batch furnaces it is advisable to shorten the nitriding process as much as possible. This makes it necessary to equip large furnaces with a system of forced cooling. 7. With nitriding in furnaces with V>0.6 m3 the major expense (up to 49%) is for electrical energy, while in small furnaces the major expense is for equipment (up to 55%).